Electromagnetic brake



Re. y21,491

June 25, 1940. P. TRoMBr-:TTA

v sLEc'rnoMAGNETIc BRAKE Original Filed Oct. 30, 1934 4 Sheets-Sheet 2 INVENTOR. K PANFLO TROMBETTA ATTORNEY June 25, 1940. P. TROMBETTA- amacrnomemz'ric BRAKE Original Filed Oct. 30, 1934 4 Sheets-Shet 5 yFIG. l2

FIG. 10.

FIG. I3

ne. |a A 79 INVENTOR.

PAN FILO TROMBETTA n BY p ATTORNEY.

June 25, 1940. P. TRoMBl-:TTA

nuzcrnoumnauc snm:

Original Filed Oct. 30, 1954 4 Sheets-Sheet 4 IN VEN TOR. PANF LO TROM BETTA lsv/www A TTORNEY Reissued June 25, 19.40

UNITED STATES PATENT OFFICE ELECTROMAGNETIC BRAKE Panlllo Trombetta, Milwaukee, Wis.

34 Claims.

This invention relates to electromagnetically operated devices of the type known as solenoid brakes and magnetic clutches. In a brake, the pressure is generally applied by springs and released by the action of an electromagnetic device of the solenoid or motor type. In a clutch, the pressure is generally applied by an electromagnetic device and released by springs. Since the two types of apparatus are very nearly the same, the term brake shall be used for the description of both throughout this specification.

'Ihe scope and usefulness of an alternating current solenoid brake is limited by limitations common to alternating current solenoids. One of the principal limitations of an alternating current solenoid is the great amount of current which it draws from the line when in open position, that is, when the solenoid is energized and its plunger is spaced from the pole piece. The current inrush is proportional to the amount of work that the solenoid can do in one stroke, so that it is not desirable to make alternating current solenoids much larger than the one that can produce about 300 inch-pounds of work per stroke. Another limitation is the high velocity at which the plunger moves even when under load.

Inherently, therefore, very large solenoid brakes cannot be operated directly by alternating current solenoids, but on the other hand, there is nothing as simple as an alternating current solenoid and therefore their use is most enticing. Medium and small size brakes, when operated by alternating current solenoids, give much trouble due to the high velocity that the plunger attains in moving to the closed or open position when the solenoid is energized or deenergized.

The present invention has as an object to provide electromagnetically operated brakes which will avoid the disadvantages set forth above.

Another object is to provide an electromagnetically operated brake which is relatively simple in construction, easy to adjust, and economical to manufacture.

Another object is to provide an electromagnetically operated brake which is capable of withstanding long and severe service without suffering undue wear on any of its parts except the friction lining. f

Another object is to provide an electromagnetically operated brake having provision for the removal and replacement of worn out linings without dismounting the brake or disturbingther adjustment thereof.

Another object is to provide an electromagneti- (Cl. 18s- 171) cally operated brake which can be removed from n capable of self alignment in both the vertical and horizontal planes.

Another object is to provide a brake which is pleasing in appearance and is capable of being mounted either directly upon the end of a motor or upon the floor as aiseparate unit.

Another object is to provide a brake which is capable of being used in connection with horizontally or vertically operated motors.

Another object is to provide abrake which can be built in any size and for any capacity up to many thousands of foot pounds without resorting to the use of unsuitable operating devices. Another object is to provide an electromagnetic disc brake with a lever mechanism to enable 'a long stroke electromagnetic apparatus to operate the brake.

Other objects and advantages will appear from the description hereinafter given of apparatus in which the invention is embodied.

In order to obtain all of the above objects and to meet the exact requirements of the industry, it is necessary to subdivide the brakes into two separate and distinct types. One, a totally inclosed brake for duties requiring neatness of appearance and which can be operated in any position and be mounted directly upon the motor. This brake is of the disc type and is not suitable for heavy duty because it cannot dissipate very much heat.l The other is a brake of the open type which is capable of dissipating large amounts of heat generated during heavy duty operation such as use upon cranes, hoists, steel mill machinery etc.

'Ihe mode of operation of these two types of brakes is very nearly the same and therefore a full explanation of one will suflice for both.

The invention is exemplified by the apparatus illustrated in the accompanying drawings in which the views are as follows:Y f

Fig. 1 is a sectional view of a disc brake which is shown mounted directly upon the end of a horizontally mounted motor, the section being taken on the line I-l of Fig. 6. The brake is shown provided with a foot for mounting it upon the floor, -but it is to be understood that the foot will be omitted when the brake is mounted directly upon the motor.

Figs. 2 and 3 are a front and an edge view of a complete brake lining holder which is preferably divided into as many segments as there are spring bolts employed in the brake in order that the lining may be renewed without disassembling the brake. As shown, the brake is provided with four spring bolts and the brake lining holder is divided into four segments each of which extends through an angular distance somewhat less than 90 in order to allow it to pass the spring bolts when renewing the lining. The brake lining holder may be made as a single circular unit if desired, in which case the brake must be partly disassembled when renewing the linings.

Fig. 4 is a detail view in cross section taken in the plane of the line 4-4 of Fig. 2 and showing the protruding pieces on the lbrake lining holder to keep it from sliding under load.

Fig. 5 is a section on the une 5 5 of Fig. 2`

and shows the way the lining is riveted on the holder.

Fig. 6 is an end view of the brake shown in Fig. l.

Fig. '1 is a side view showing the brake casting of the brake shown in Fig. 1 provided with openings through which the brake lining holder segments may be removed and replaced.

Fig. 8 is a vertical section through a cover for disc brakes such as that shown in Fig. 1, the hand release lever being mounted on the coverl instead of on the bridge casting as shown in Fig. l.

Figs. 9, yl0, 11, and 12 are detail views showing two ways to' take up the wear on the lining.

Figs. 13 and 13A are views showing another construction of a double lever system used in connection with these brakes.

Fig. 14 is an end view and Fig. 15 is a. side view of another embodiment of my invention in .which the entire brake is supported by and floats amounts of heat are to be dissipated, the brake is provided with an open casing instead of a closed casing as shown.

Figs. 1 t0 6 In Fig. l, a disc brake is shown mounted upon a motor I by means of an adapter casting 2. The adapter 2 is entirely separate from the motor and from the brake casting 4. When the brake is to be mounted upon the floor, a foot 3 is cast integral with, or in vsome cases separate from the brake casting 4. separate casting, the brake is mounted on it in a manner similar to the way it is mounted on the adapter casting. A cover or bridge 5 is bolted to the casting 4 by means of three or tour machine screws not shown in the drawings.

The brake mechanism consists of a friction lining holder 21 to which is riveted a lining 49, a rotating steel disc 29, another friction lining holder 29 having a friction lining attached to each side thereof; another rotating steel disc 39 and another lining holder 29 to which is also attached a friction lining. This forms what is known as a double disc brake. On top of all this is what is known as a pressure bell 25. On the top of the pressure bell` is a set of2 or 4 springs 2l held tightly against the pressure bell by bolts 22,

When the foot is made in a.

Thus the rotating discs 29 and 39 are compressed between the four friction linings by the springs 2|. As shown in Figs. 1 and 6, the bell 29 is provided with a threaded boss having a stud 24 threaded therein and extending through a slot formed in a lever 9 which is connected to the stud 24 by a pin 49. The lever 9 is arranged between two-posts 23 which are fastened to or formed integral with the bridge 9 and to which the lever 9 is pivoted by means of a pivot pin 41.

The lever 9 has its upper endarranged between the two arms or sides of a bifurcated lever III which has its lower end connected to the lever 9 by a pin II and its upper end arranged behind or to the left of a stop or shock absorber 9 arranged between and fastened to two plates 9 which extend outward from the bridge 5 and are fixed thereto or formed integral therewith.

The lever I9 intermediate its ends is connected by a pin 49 to the armature I3 of a solenoid .which has its frame attached to the bridge 5 and is of the movable pole piece type described in my copending application Serial No. 738,571, filed August 6, 1934.

'I'he outer end of the armature I3 extends between and beyond the arms of the lever I9 and is connected by a spring I2 to a lug Ill'l which connects the two arms of the lever I9 to each other and overlies the upper end of the lever 9.

The arrangement is such that the lever I is free to swing to the right without operating the lever 9 but, when it is swung to the left by the solenoid, the lug III* will engage the upper end of the lever 9 and swing it to the'left to releas the brake.

As shown, the lever 9 extends below the stud 24 and encircles a bolt 35 which extends through the bridge and has a nut 39 threaded upon its outer end and a spring encircling it between the nut 39 and the lever 9. The pressure of the spring 20 is transmitted to the pressure bell by the lever 9, pin 49 and stud 24 so that the spring pressure may be applied either directly by the springs 2| or through the lever system by spring 20 or by both sets of springs jointly.

The operation of the brake is as follows: When the solenoid is energized the plunger I3 is attracted to the left until it touches the pole piece I5. When the pole piece I9 is struck by armature I3 it recedes to the left by reason of the elongated hole I9 until the lever I0 strikes a shock absorber 49 which' is arranged upon the bridge 5 and made of a suitable slightly resilient material. Both the lever I9 and the plunger I3 must then come to a stop and the energy stored in the moving plunger I3 and the arm Ill is dissipated in lshock 'absorber 49. By this time the pole piece I5 is adhering tightly to the ends of the plunger I3 and the springs of the brake pull lever I0, armature I3 and pole piece I5 to the right until pole piece I5 is stopped by the pin II.

When the solenoid is deenergized the springs 29 and/or 2| cause the lever I9 and the plunger I3 to ily back to the right. When the discs are compressed the lever 9 cannot move farther to the right but lever I9 due to the speed which it has acquired and swinging on pin II will keep on moving to the right until it is stopped by the shock absorbing device.9. The energy stored in lever I9 and armature I3 is, therefore, absorbed by shock absorber 9 and is not reected back to the pressure bell 29. In this way is avoided a shock or Jerk which would be caused by such reilected blow on stud 24 and bell 25.

The lever ratio of this brake is the ratio of the distance between pins 41 and 48 divided by the distance between pins 46 and".

The spring lz has nothing to do with the brake pressure but is used to balance the weight of armature I3 so that this weight will not bear upon the armature guide' I9.

It will be noted that the amature I3 is connected to the lever I|I without the interposition of a loose link. This construction makes it possible for the brake to operate with the solenoid mounted in a horizontal position as shown in Figure 1, because if an intermediate link were interposed the link would collapse and cause the plunger or armature to bind in the solenoid. Thus it may be stated that the combination of the use of the spring I2 and the direct mounting y of the plunger renders this brake capable of operating in all positions and the operation is as efficient in one position as it is in any other when the spring is adjusted for the particular position.

As the linings wear the arm Il) will move farther and farther to the right until it 'will actually touch 9 and then the brake will begin lto slip. In order to readjust the brake it is necessary to remove pin 46 and unscrew stud 24 an amount equivalent to the total wear on lining.

The torque of the brake is taken entirely by the bolts 22 of which sometimes there are 4 and sometimes only 2. The use of only two bolts and two springs makes it easier to remove worn out linings and replace new ones. Thus when only two bolts are used the removable rings shown in Fig. 2 have to be cut into segments of 180 while if four bolts are used they have to be cut into segments of 90. 'I'he bolts 22 float on casting 4 and cup washer SII which ts over the spring 2| and inside the spring housing 50A.

In order to allow axial movements of the motor shaft the discs 29 and 30 float on hub 3| which is rigidly fastened and keyedto the shaft 33.

The hub 3| in one of the embodiments of my invention is made of square cross section and ts into a square hole in discs 29 and 30.

In Fig. 1 the stationary friction lining holder 26 is shown with the lining riveted directly on it but it may be provided with recesses similar to those provided on the bottom of casing 4 and on the bottom of pressure bell to admit the replaceable units shown in Fig. 2.

In order to make it possible to release the brake by hand, a hand release lever I is provided. 'I'his lever shown in its preferred form mounted on bridge 5 in Figs. 1 and 6 is sometimes mounted on the overall cover of the brake as shown in Fig. 8. The operation of the lever in both cases is as follows: When the uppermost part of this lever is pressed downward the lower part 1a impinges on lever 6 and pushes it to the left and' thereby performs the same function as the solenoid when it is energized.

In accordance with the embodiment of my invention shown in Fig. 1 the solenoid is made of theE type. These solenoids are more suitable for short strokes and when made to seal on all of the three legs are the most Vquiet solenoids that can be made.

According to the prior art these solenoids arev with a gap in the middle leg and sealing on all three legs represents va great advancement in when quietness of operamotive force supplied by the molecular varrange-y ment of the steel. The flux producing the sticking force may, therefore, be calculated by dividing the residual magnetomotive force by the reluctance of the magnetic circuit. 'I'he seat of the residual magnetomotive force is located at a point in the magnetic circuit which is near the 'center of the coil since the maximum density of the ux is at this location. By cutting the magnetic circuit at or near the center of the .coil,

where the greatest density of flux exists, the;

residual megnetomotive force is substantially destroyed and all or most of the sticking effects are eliminated.

This is accomplished by dividing thel middle leg of the armature into two sections which are separated from each other by an air gap I4, as shown in Fig. 1. The armature consists of a stack of E-shaped laminations, a stack ofshort laminations arranged in alinement with but spaced from the middle leg of the E-shaped laminations, and two heavy' E-shaped non-magnetic plates between which all of the laminations are riveted and which bridges the gap I4 to hold the short laminations in position. The end laminations are made as short as possible ,but long enough to receive two rivets which keep them in alinement. If the armature is very thick, it is ordinarily provided with a third heavy E-shaped plate which extends through both stacks of laminations midway between the two outer plates.

In order to make it possible for the removal of worn out linings and the replacement of new ones the brake housing 4 is made with suitable openings on each side, as shown in Fig. 7.

Each of the renewablev friction lining units shown in Figs. 2, 3, 4 and 5 consists of a lining 40 and a lining carrier 4| and ordinarily extends through an angular distance somewhat less than the angular distance between adjacent spring bolts. The carrier 4I has the lining 40 riveted to one face thereof by countersunk rivets 44 and the other face thereof provided with projections 42 to t into recesses 43 formed in the inner end wall of the casing 4 and the lining holders 26, 21, and 28. As shown, the projections 42 are formed by partially punching out small sections of the carrier 4I.

When the brake is provided with a lever mechanism of the simple lever type as shown in Figs. 1 and 6, it is not ordinarily possible to obtain a lever ratio greatly in excess of 8 to 1 without making the brake clumsy and out of aesthetic proportions. This ratio is sufiicient only when a very short-stroke solenoid is employed.

In actual practice, it is found that the lever mechanism must have a much greater ratio which can be obtained by using la compound lever mechanism such as that shown in Figs. 13 and 13A.

This lever mechanism consists primarily of a double outer lever 'I5 and a double inner lever.

I6 arranged between the two sides thereof. The lever 15 has its right end connected by a pin I4 to an electromagnetic apparatus, such as the armature Il, and its left end straddling and pivoted by a pin 1| to avstationary. post 11 which is carried by the frame or casing of the brake and corresponds to the. two `posts I shown in Fig. 1. l

' 'I'he lever 16v straddles rand is pivoted intermediate its ends by a pin 13 to a stationary post 1l which is carried by the frame or casing of the brake and corresponds to the post 23 shown in Fig. 1. The left end of the lever 15 is pivoted by a pin 59 to the lever 15 near the pin 1|. The

, right end of the lever 16 straddles and is connected by a pin 12 to a stud 19 which is connected to the pressure member of the brake and corresponds to the stud 24 shown in Fig. 1.

When the right end of the lever 15 is pulled downward in respect to Fig. 13A by the electromagnetic apparatus, the pin 69 moves the left end of the lever 16 downward and thereby causes the right end thereof to move upward.

By employing compound levers, ratios up to 70 to 1 may be obtained for mediumsize brakes and up to 120 to 1 for large brakes.

Instead of connecting the stud 19 to the lever 16 by means of pin 12 as shown in Figs. 13 and 13A, .the stud may be provided upon its outer end with a nut which is pivoted upon the outer edges or top of the lever 16, as shown in Figs. 9 to 12.

In Figs. 9 and 10, the stud is indicated by the reference numeral |20 and shown provided with a nut ||9 having a plurality of grooves formed in its under face to be engaged by two arcuate projections or bearings which are fastened upon the upper edges of the lever 16.

In Figs. 11 and 12, the stud is indicated by the reference numeral |22 and shown as having its upper end slotted and a nut |23 threaded thereon. 'I'he nut |23 has a plurality of grooves formed in its under face to be engaged by a pin |24 which extends through the slotted upper end of the stud and bears upon the upper edges of the lever 1I.

In either case, the brake may be adjusted by turning the nut ||9 or |23, the brake springs permitting the nut to rise and fall as the grooves pass into and out of alinement with the projections |2| or the pin |24. After adjustment is f made, the grooves prevent the nut from being turned accidentally.

In Fig. 7 is shown a side view ofthe same brake shown in Fig'. 1 in order to show the openings at the side for the purpose of removing the removable lining holder units shown in Fig. 2. Many of the parts of the brake are left out for the sake of clarity. In this case the brake has four springs and spring bolts and the removable units-are, made in segments of less than 90 so that they can pass between the bolts |59. This particular model is provided with only two openings although more may be provided if desirable. In this case the upper `and lower segments must be slid around the circumference until they come in front of the openings. Sometimes the brake is made with only two segments placed diametrically opposite each other. This is possible in case of very light duty brakes where the wearing of the lining is of no consequence.

Fig. 8 shows in cross-section a removable cover which is sometimes employed to cover the brake mechanism to improve the appearance thereof and in the interest of safety.

'I'he cover consists primarily of a hollow cast iron body 55 which is sometimes made large enoughl to cover the entire mechanism including the solenoid. At other times it is made substantially the same size as bridge in which case it has a slot 56 formed in its side wall to clear plates I and lever Il, and a separate cover is arranged over the solenoid. f

The cover may be xed in position in any suitable manner such as by means of bolts 51 each of which extends through the top of body 55 and is threaded into holes 5l formed in bridge 5. Each bolt 51 has a tubular separator 59 arranged thereon to space the cover from bridge 5.

In order that the brake may be manually released when the cover is in position, a release lever 1 is pivoted to the end wall of the cover and extends through a slot 66 formed therein. Lever 1 is substantially vthe same as lever 1 and is provided upon its inner end with an armr1A` to depress lever 6 when lever 1' is swung upon its pivot.

Figs. 14 and 15 disclose another method of mounting the brake shown in Figs. 1 to 6. This method diifers from the previously described method in that the rotatable friction disk is fixed to the rotatable member or motor shaft, instead of being splined thereon as in Fig. 1, and the brake casing is mounted upon stationary guides which permit the entire brake to float and thereby compensate for end play of the rotatable member or motor shaft and which permit the rotatable and nonrotatable disks to move axially relative to each other as the brake is applied and released.

As shown, the adapter casting 2 of Fig. l is replaced by an adapter casting 2' having two diametrically opposed arms |58 which are flanged at the free ends thereof. The brake frame or casting 4 is arranged between the arms |58 and retained in position therebetween by two bolts |54 each of which extends through the flanged outer end of an arm |58 and through the casting 4 and is threaded into a boss |55 formed on the adapter casting 2 alongside the arm |58.

Each bolt |54 is closely fitted in two holes |56 and |51 formed in the end walls of the casting 4 so that the entire brake is free to move axially or to float upon the bolts |54 but is restrained from rotation thereby.

For the purposev of illustration, the brake is shown provided with the compound lever mechanism disclosed in Fig. 13 but it may as' readily be provided with a different type of lever mechanismas shown in Figs. 1 and 6.

'I'he invention herein set forth is susceptible of various modifications and adaptations without departing` from the scope thereof as hereafter claimed. The invention is hereby claimed as follows:

1. An electromagnetic brake for a rotatable member, comprising a stationary frame, a nonrotatablebraking element arranged within said frame and restrained from movement relative thereto, a second non-rotatable braking element slidable within said frame and restrained from rotation thereby, a rotatable braking element arranged betweensaid non-rotatable elements and connected to said rotatable member to rotate therewith, spring means for applying said brake, a single pressure member for transmitting the pressure of said spring means to said braking elements to force all of them together, a lever mechanism connected to said pressure member and pivoted to said frame for relieving said pressure member from the pressure of said spring means, a single solenoid attached to said frame and having its armature connected to said lever connected tosaid rotatable member to rotate` therewith, spring means for applying said brake, a single pressure member for transmitting the pressure of said spring means to said braking elements to force all of them together, a lever mechanism connected to said pressure member and pivoted to said frame for relieving said pressure member from the pressure of said spring means, a single electromagnetic apparatus for operating said lever mechanism and including a magnet and an armature one of which is attached,

to said frame and the other of which is connected to said lever mechanism at one end thereof to operate it in a direction to release said brake, and a spring connected to said lever mechanism at the other end thereof to apply pressure to said pressure member.

3. An electromagnetic brake for a rotatable member,'comprising a stationary frame, a nonrotatablc braking element arranged Within said frame and restrained from movement relative thereto, a second non-rotatable braking element slidable within said frame and restrained from rotation thereby, a rotatable braking element arranged between said non-rotatable elements and connected to said rotatable member to rotate therewith, spring means for applying said brake, a single pressure member for transmitting the l pressure of said spring means to said braking elements to force all of them together, a lever mechanism connected to said pressure member and pivoted to said frame for relieving said pressure member from the pressure of said spring means, a single electromagnetic apparatus for operating said lever mechanism and including a magnet and an armature one of which is attached to said frame and the other of which is connected to said lever mechanism, a removable cover arranged upon said frame over said lever mechanism, a pivot carried by said cover, and a hand release lever carried by said pivot and operable from the outside of said cover to engage said lever mechanism and operate it to relieve said pressure member from the pressure of said spring means.

4. An electromagnetic brake as set forth in claim 1, characterized by said frame having a lateral opening therein, said non-rotatable braking elements having a plurality of segmental brake lining carriers held against rotation thereon and readily removable radially therefrom through said opening, and each of said carriers having a facing of brake lining material fixed to one side thereof.

5. An electromagnetic brake as set forth in claim l, characterized by the lever mechanism including a compound lever to obtain a very large lever ratio between said electromagnetic means and said pressure member.

6. An electromagnetic brake for a rotatable member comprising a stationary casing, a nonrotatable braking element arranged within said casing and restrained from movement relative thereto, a second non-rotatable braking element slidable. within said casing and restrained from rotation thereby, a rotatable braking element arranged between said non-rotatable elements and connected to said rotatable member to rotate therewith, a single pressure member slidable within said casing for transmitting pressure to said braking elements to force the same together,

a plurality of springs acting upon said pressurev member forA applying pressure thereto and having the axes thereof parallel to the direction of movement of said pressure member, a lever mechanism connected to said pressure member and pivoted to said casing for relieving said pressure member from the pressure of said springs, a solenoid having its frame attached to said casing and its armature slidable in said frame and connected by a pivot to said lever mechanism to operate the same upon said solenoid being energized, and a spring having one of its ends connected to said lever mechanism and its other end connected to said armature at a point outward from said pivot to prevent said armature from binding in said frame and to avoid undue wear of said solenoid when said brake is arranged in such a position that said solenoid is horizontal.

'7. The combination, with a shaft rotatable in a stationary casing, of an electromagnetic brake comprising a plurality of supports fixed to said casing, a frame slidable upon said supports and restrained from rotation thereby, a non-rotatable braking element arranged within said frame and restrained from movement relative thereto, a second non-rotatable braking element slidable within said frame and restrained from rotation thereby, a brake disk ilxed on said shaft to rotate therewith and restrained from movement axially thereof, spring means for applying said brake, a pressure member for transmitting the pressure of said spring means to said braking elements to force all of them together, a. lever mechanism connected to said pressure member and pivoted to said frame for relieving said pressure member from the pressure of said spring means, and electromagnetic means for operating said lever mechanisms to relieve said braking elements from the pressure of said spring means.

8. 'I'he combination, with a shaft rotatable in a stationary casing, of an electromagnetic brake comprising a plurality of supports fixed to said casing, a frame slidable upon said supports and restrained from rotation thereby, `a non-rotatable braking element arranged within saidframe and restrained from movement relative thereto, a second non-rotatable braking element slidable 'within said frame and restrained from rotation thereby, a brake disk iixed on said shaft to rotate therewith and restrained from movement axially thereof, spring means for applying said brake, a single pressure member for transmitting the pressure of said spring means to said braking elements to force all of them together, a lever mechanism connected to said pressure member and pivoted to said frame for relieving said pressure member from thev pressure of said spring means, and a single electromagnetic apparatus for operating said lever mechanism and including a magnet and an armature one of which is attached to said frame and the other of which is connected to said lever mechanism.

9. An electromagnetic brake as set Iorth in claim 7, characterized by thee-lever mechanism including a compound lever to obtain a very large lever ratio between said electromagnetic means and said pressure member. y y

10. The combination, with a rotatable meinber, of a disk brake comprising a casing having rear and side walls extending around said member and a front wall extending across its side wall, two non-rotatable braking elements arranged within said casing and restrained from rotation relative thereto, a rotatable braking element arranged between said non-rotatable elements and connected to said rotatable member to rotate therewith, a non-rotatable pressure element arranged within said casing to transmit spring pressure to said braking elements, a plurality of bolts arranged around the outside of said rotatable element ,and extending through said rear wall and through at least one of said non-rotatable elements to take the torque thereof during application of said brake, each of said bolts being restrained by said front andv rear walls from movment transverse to the bolt axis, an abutment fixed upon the front end of each bolt, a compression spring encircling each bolt between said abutment and said pressure element for forcing said braking elements together to thereby apply said brake, a lever mechanism connected to said pressure element and pivoted to said casing. for retracting said pressure element to thereby relieve said braking elements from the pressure of said springs, and a single electromagnetic apparatus for `operating said lever mechanism and including a magnet and an armature one of which is fixed in a stationary position in respect to said casing and the other of which is connected vto said lever mechanism.

11. The combination, with a rotatable member, of a disk brake comprising a casing having rear and side walls extending around said member and a front wall extending across its side wall, two non-rotatable braking elements arranged within said c'asing and restrained from rotation relative thereto, a rotatable braking element arranged between said non-rotatable elements and connected to said rotatable member to rotate therewith, a non-rotatable pressure element arranged within said casing to transmit spring pressure to said braking elements, a plurality of bolts arranged around the outside of said rotatableV element yand extending through said rear wall and through at least one of said non-rotatable elements to take the torque thereof during application oi said brake, each of said bolts being restrained by said front and rear walls from movement transverse to the bolt axis,

an abutment fixed upon the front end of each` bolt, a compression sring encircling each bolt between said abutment and said pressure element for forcing said braking elements together to thereby apply said brake, a lever mechanism connected to said pressure element and pivoted to said casing for retracting said pressure element to thereby relieve said braking elements from the pressure of said springs, and a solenoid having its frame fixed in a stationary position in respect to said casing and its armature connected directly to said lever mechanism to operate the same upon said magnet being ener- Sized.

12. The combination, with a rotatable member, of a disk brake comprising a casing having rear and side walls extending around said member and a front wall extending across its side wall, two non-rotatable braking elements arranged within said casing and restrained from rotation relative thereto, a rotatable braking element arranged between said non-rotatable elements and connected to said rotatable member to rotate therewith, a non-rotatable pressure element arranged within said casing to transmit spring pressure to said braking elements, a plurality of bolts arranged around the outside of said rotatable element and extending through said rear wall and through at least one of said non-rotatable elements to take the torque thereof during application of said brake, a plurality of sockets fixed to said front wall, an abutment fixed upon the front end of each bolt and arranged in one of said sockets, a compression spring encircling each bolt between said abutment and said pressure element for forcing said braking elements together to thereby apply said brake, a lever mechanism connected to said pressure element and pivoted to said casing for retracting said pressure element to thereby relieve said braking elements from the pressure of said springs, and

, a single electromagnetic apparatus for operating exert a braking force thereon, the combination of a plurality of segmental brake lining unitsr each comprising a backing member and a friction member arranged upon one of said elements, and means for attaching said backing members to that element to be readily removable radially l therefrom withoutl removing any of said elements from said shaft. v

14. In a brake having rotatable and no-rotatable braking elements arranged around a shaft Y to exert a braking force thereon, the combination of a plurality of segmental brake lining units each comprising a backing member and a friction member arranged upon the non-rotatable elements, and means for attaching said backing members to said elements to be readily removable therefrom without removing any of said elements from said shaft..

l5. In a disk brake for a shaft, the combination of a plurality of iiat braking elements arranged around said shaft, one of said elements having a plurality of sockets arranged therein, a plurality of segmental brake lining units arranged between the socketed element and the adjacent element, each of said units comprising a backing member and a friction member, and a anism for releasing the brake against the action of said spring means, and electromagnetic means for operating said lever mechanism, the combination of a hollow cover arranged upon said frame over said lever mechanism, and means carried by said cover and operable manually from the outside thereof to operate the lever mechanism inside said cover to release the brake.

17. In a brake having a housing, rotatable and non-rotatable braking elements arranged within f compressing said two sets of rotatable and nonnism in said housing for releasing the brakev against the action of said spring means, the combination of electromagnetic means for operating said lever mechanism and means operable manually through an opening in said housing to operate the lever mechanism insldelsad housing to release the brake. l

19. An electromagnetic brake comprising a plurality of rotatable discs interposed in cooperative position with a plurality of non-rotatable discs, an end pressure plate, spring means for rotatable discs together and a lever mechanism for releasing said spring pressure, and electromagnetic means for releasing said spring pressure, said electromagnetic means having its moving member movable in a horizontal trajectory and connected to a lever for releasing said brake, said moving member being provided with a projection beyond its connection to said lever, and

spring means connected between said projection and a lug on said lever to counterbalance the weight of the moving member, eliminate wear upon its guides, and prevent it from binding due to improper alignment.

20. An electromagnetic brake comprising a plurality of rotatable discs interposed in cooperative position with a plurality of .non-rotatable discs, an end pressure plate, spring means for compressing said two sets of rotatable and nonrotatable discs together and a lever mechanism comprising a plurality oi' levers for releasing said spring pressure, electromagnetic means for releasing said spring pressure, the last lever in the lever system being provided with a lug suitably located and drilled to receive one end of a spring, the other end of said spring being connected to a projection provided at the outer end or! a solenoid plunger in such a way that when the solenoid operates in a horizontal position the weight of the plunger is relieved by the pressure of the spring.

21. In a brake having rotatable and non-rotatable braking elements arranged around a shaft to exert a braking force thereon, the combination of a plurality oi' removable friction lining units each comprising a backing member and a friction member fastened to said backing member and having on the side opposite from the lining projections which will tit in cooperatively located depressions in the non-rotatable elements of thegbrake in such a way that the umts can be readily removed from such a position for the purpose of replacing the lining, said projections keeping said lining units from sliding under the inuence of the rotating discs.

22. An electromagnetic disc brake comprising a cylindrically shaped casing partially opened at one end and wide open at the other end provided to and near the cylindrical wall making anchor on the bottom and on the removable cover when said cover is in place, a plurality of rotatable discs arranged within said casing in cooperative relation with a plurality of non-rotatable discs, said non-rotatable discs being slidably mounted upon said plurality of rods, in such a way that said rods take the torque and restrain said nonrotatable discs i'rom rotation, an end pressure plate in cooperative relation with said rotatable and non-rotatable discs to apply pressure thereon, a lever mechanism fulcrumed upon said removablev cover and connected to said pressure plate, and a solenoid connected to said lever mechanism in opposition to spring means biasing said lever, said spring means normally holding said parts in braking relation and said solenoid effecting release thereof. l

23. An electromagnetic disc brake substantially as described in claim 22 having a lever system composed of two levers, one of said levers being fulcrumed at a point on the removable cover near the center and having a part thereof connected to the pressure plate, the other of said levers being fulcrumed at a point near the outer edge of said cover and being connected at a point near lts fulcrum to the other end of said rst lever to obtain a large lever ratio, the other end of said second lever .being connectedto the solenoid, lever system and solenoid being connected in cooperative relations to the pressure plate and springs to cause brake release by energization oi' solenoid.

24.v An electromagnetic disc brake substantially as described in claim 22 characterized by being provided with two sets of springs, one set oi' springs being mounted upon lthe torque rods and the other set of springs being mounted external to the lever mechanism, the first set being used to provide a portion oi' the required spring pressure and the second set for providing the remainder of the requirements.

25. An electromagnetic disc brake substantially as described in claim 22 characterized by being provided with two sets of springs, one set` of springs being mounted upon the torque rods for supplying a minimum unvariable amount o1' the total pressure requirements, the other set being mounted external to the lever system for supplying the diiierence between the minimum and maximum pressure requirements, this last set oi' springs being made readily adjustable.

26. An electromagnetic brake comprising rotatable elements interposed in cooperative relations with non-rotatable elements, spring means ior compressing said non-rotatable elements against said rotatable elements, a lever system for releasing said spring pressure, said lever system comrising a plurality oi' levers, one end oi' connected to an electromagnetic means which when energized will act to release said spring pressure, the lever to which the solenoid is attached being made in two parts and constructed and assembled in such a way as will allow the moving part of the solenoid to travel its full stroke at all times irrespective of the amount of wear of the friction lining oi said brake, and means for restricting the oscillating amplitude oi' said lever under the iniiuence of electromagnetic and spring i'orces within predetermined limits as imposed by the maximum stroke of the solenoid and the desirability oi' protecting said solenoid from the impact of the moving plunger and lever mechanism.

27. In a device oi' the class described, a clutch or brake mechanism adapted to be moved alternately into open and closed positions, and a solenoid operating in opposition to other means for moving said mechanism into and out of closed position, said solenoid having an armature extending substantially through the center of the solenoid winding, said armature being provided with a predetermined air gap resistance to the iiow\\of magnetic iiux therethrough to prevent residual magnetism from sticking the armature and thereby failing to effect operation of said mechanism. l

28. In a device of the class described, a solenoid having a movable plunger extending through the center of its winding and adapted to contact with other parts to provide a closed magnetic circuit, said plunger being provided with a restriction to the flow of magnetic iiux at a point remote from the contact surface thereof to prevent residual magnetism fromfrestraining movement of the plunger.

29. In a device of the class described, a solenoid comprising a winding disposed with its axis horizontal and mounted on a base forming part of the circuit for magnetic flux, said base being supported for limited movement axially of the winding, an armature movable axially of said winding to close the magneticy circuit with said base, said armature being pivoted at its outer end on mechanism to be operated by its movement, and means to counterbalance at least in part the weight oi said armature on said pivot.

30. In an electromagnetic brake, a brake mechanism, a housing therefor, a solenoid mounted on said housing with its winding disposed for limited axial movement in a horizontal direction and having a plunger movable in the same directicn but through a greater distance, means for supporting said plunger at its outer end and connecting it to said brake mechanism to operate the same, and means for counterbalancing the weight of said armature to keep it in axial alignment with said winding.

31 In an electromagnetic brake, a brake mechanism, a housing therefor, a solenoid mounted on said housing with its winding disposed for limited axial movement in a horizontal direction and having a plunger movable in the same direction but through a greater distance, means for supporting said plunger at its outer end and connecting it to said brake mechanism to operate the same, means for counterbalancing the weight of said armature to keep it in axial alignment with said winding,- and means on said housing for limiting the movement of said armature when the winding is energized to cushion the stroke of the solenoid. i

32. In a device of the class described, a solenoid disposed with its axis at an angle to the vertical and having a movable plunger for operating a lever, said plunger being connected -to said lever and at least partially supported thereby, and means on said lever for counterbalancing at least a part of the weight of said plunger on said connection.

33. In a disc brake ofthe class described, a plurality of springs disposed around the discs for pressing the same into engagement, said springs being adjusted to provide substantially equal `brake pressure around the circumference of said discs, a lever mechanism connected axially of the brake to compress said springsand release said brake, and a second spring member operating on said lever mechanism to apply additional pressure to the brake and disposed for ready adjustment 'for taking up the wear of the brake lining unipressure on said discs against said spring pressure. 45

PANFILO TROMBETTA. 

